Ever increasing data processing requirements demand faster and denser random access memory to keep pace with improved CPU speed and throughput. Semiconductor memories such as dynamic RAM and static RAM have very fast access times but are also volatile. Electrically erasable/programmable read only memories (EPROMs) are nonvolatile but have very long write times and offer a conflict between refresh needs and radiation tolerance. A ferroelectric RAM (FRAM) offers short read and write access times, but the data retention (nonvolatility) and the longevity of the ferroelectric material (reliability) are in question. The magneto-resistive random access memory (MRAM) is nonvolatile and has no problem with longevity but has long read access times (on the order of microseconds). None of the existing technologies can satisfy all of the needed data storage requirements. An objective of this invention is to provide an integrated fast access (&lt;100 nsec), nonvolatile, radiation hard, high density (&gt;10.sup.6 bit/cm.sup.2) random access memory for high speed computing using magnetic material for storage and Hall-effect sensors for reading out data stored.
It is noted that the concept of using magnetic material for a nonvolatile RAM has been implemented before, e.g., in core memory, cross-tie memory and the recent magnetic random access memory (MRAM). The Hall effect has also been used since it was discovered in 1879 to detect small magnetic fields. What has not been conceived heretofore are memories which combine magnetic storage with Hall-effect sensing to form what is referred to herein as magnetic-Hall random access memory MHRAM. Recent improvements in InSb deposition processing and technology, and recent studies on very small and thin permalloy particles, currently make possible the implementation of the novel MHRAM concept for high density, fast access, nonvolatile, radiation hard, random access memory.